Defect Donor and Acceptor in GaN

High-energy (0.7 endash 1MeV) electron irradiation in GaN grown on sapphire produces shallow donors and deep or shallow acceptors at equal rates, 1±0.2 cm-1. The data, in conjunction with theory, are consistent only with the shallow donor being the N vacancy, and the acceptor the N interstitial. The N-vacancy donor energy is 64±10 meV, much larger than the value of 18meV found for the residual donor (probably Si) in this material. The Hall-effect measurements also reveal a degenerate n -type layer at the GaN/sapphire interface which must be accounted for to get the proper donor activation energy. copyright 1997 The American Physical Society